hottest workout trends. Does it make you bigger instead smaller. Tracy anderson landed in the hot seat after saying spinning bulks you up. She's here with the skinny on the exercise. ? Nice one, robin. I am a fan of spinning but you can call it the clash of the exercise titans, but fitness entrepreneur tracy anderson sat down with me to clear up the swirl of controversy that spun out over what she says spinning can or cannot do for your body. &#9834; she's the fitness guru to the stars like gwyneth paltrow and madonna. So you just rotate up. Reporter: Not to mention the thousands of noncelebs who train in her studios but its comments tracy made about the wildly popular indoor cycling craze that now has some heads spinning. Anderson telling "redbook" online, spin may burn calories in the authority time but if that's all you're doing it'll bulk your thighs. They are comments were distorted, she said and spun out of control. Never said that spinning makes you fat. Reporter: Many defend it. One of the fastest growing fitness trends out there. Is it possible it could actually add inches? Here we go. Reporter: Instructors at the popular spinning chain flywheel says that just won't happen if you're doing it right. We know cuss on strong, long lean bodies and, you know, we have countless stories of weight loss from our riders. Reporter: Meredith tepper started spinning six months ago and says her body has changed for the better. My muscles have been toned a little bit more. My legs have definitely gotten stronger. Reporter: But not bulkier per se. Not bulkier. Doing one exercise over and over again is not going to bulk you. It will help shape the muscle. Reporter: Some in the fit ins community taking issue with her use of the word "bulk" and says it draws a negative connotation. Using bulk and bigger and stronger are not looked at as women shouldn't be that way. Reporter: Anderson prefers balance over bulk and isn't afraid to speak out about it. The truth is is that it takes a lot of care and attention to achieve your best body. Reporter: There is no quick fix. There is no quick fix. Reporter: Now, tracy doesn't rule out spinning altogether because she knew I was a fan. Don't give it up if it motivates you and gets you moving. Fitness pros shouldn't be fighting each other, they should be fighting the common enemy which is the couch. Cardio is a good thing. She said balance and moderation. The couch is an ally. Spinning is really hard. Always good to see you, juju. Thank you so much.

This transcript has been automatically generated and may not be 100% accurate.

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